Phototube



May 14, 1935.

Dfc. LAW

' PHOTOTUBE Filed NOV. 30, 1951 fizaerzfor fizz/9. C'Zaw, aceased Adina.

BY MTTOR EY Patented May 14, 1935 "TENT FFlcs 2,001,685 PHOTOTUBE.

Dufli Law, deceased, late of Philadelphia, Pa., by JanetF. Law,administratrix, Philadelphia, Pa, assignor to United Research.Corporation, Long Island City, N. Y., a corporation of DelawareApplicationNovember 30, 1931, Serial No. 578,016 4 Claims. (cream-27.5)

This: invention relatestophoto electric tubes, andparticularlytomultiple element photo-tubes.

Difliculty has been experienced in getting satisfactory response fromphoto-tubes to fluctuating light beams having fluctuation frequenciesvarying over the entire audible frequency range.

Anobject of this invention is to combine a plurality of.photo-responsive elements in a single photo-tube structure in which thevarious elements are respectively more sensitive to different ranges ofthe audible sound spectrum.

Another object of this invention is to combine in a photo-tube aplurality of separately photoresponsive elements.

Still another object is to combine in a phototube separatephoto-responsive elements of different photo-responsive materials.

A further object of this invention is to combine a photo-tube with arecord system in which the recorded frequencies are subdivided intogroups or ranges of frequencies, and the phototube is adapted to respondto the groups of frequencies through separate responsive elements.

A still further object of this invention is to incorporate into aphoto-tube a plurality of photo-responsive materials.

Still a further object of this invention is to utilize a plurality ofphoto-responsive alkaline metals, including potassium, sodium, caesium,lithium and other members of the alkali and alkaline earth metal groups.

Previously constructed photo-tubes have customarily utilized but asingle photo-sensitive material, usually potassium or potassium hydrideupon suitable electrodes within an evacuated container.

It is found that the various alkali, and alkaline earth metals aredifferently responsive to light fluctuations within different frequencyranges.

This invention provides a photo-tube and record system in which thephoto-tube has a plurality of cathodes respectively composed ofdifferent photo-responsive metals, such as potassium, sodium, lithium,casium, etc., which are adapted to be connected in a single circuit orin separate circuits, and may be separately responsive to separatefrequency records. The record may desirably consist of a plurality oftracks in separate frequency ranges upon a single film, the separaterecord tracks respectively cooperating with the separate cathodes in thesingle tube.

This invention thus provides a new and useful photo-tube construction,adapted to cooperate with a multiple-track record for the production ofa superior and improved sound transcription.

Other objects and structural details of the invention will be apparentfrom the following clescription when read in connection with theaccompanying drawing in which:

Fig. l is a top View of a photo-tube and record embodying thisinvention,

Fig. 2 is a front view of the same embodiment, and

Fig. 3 is a side View of the same embodiment.

-Referring to the drawing, an evacuated container I is provided having aplurality of cathode electrodes 2, 3, and l, and a single filamentaryanode 5.

The anode 5 is desirably supported by lead wires 5 and l passing througha press to contactprongs carried in a base 8 as shown. The cathode 2 maybe carried upon a lead wire 9, the cathode 3 upon a lead wire it, andthe cathode 4 upon lead wire ll, all of which likewise pass through thepress to prongs in the base 8 as shown.

Shield members l2 and it of insulating material are positioned betweenthe respective cathodes 2, 3 and 4 and may be supported therefrom, ormay be supported in any other convenient way.

Alternatively, the shields may of course be positioned outside of thetube, and so arranged as to separate the beams of light to therespective cathodes.

In constructing the photo-tube of this invention, the press and leadwires may be prepared in the usual way, with the cathode supports andanode attached to the lead wires. The respective cathodes may then beprepared by applying the appropriate alkali or alkaline earth metal inthe form of a coating upon the supports. This is preferably done undernon-oxidizing conditions, as under a blanket of nitrogen or carbondioxide or in a vacuum, by methods which are well known to those skilledin the art. After application of the photo-responsive metals to thecathode support structures, the mount with cathodes and anodes may besealed; into the container I which is thereafter evacuated by well knownmethods, which may include appropriate baking out steps. However, caremust be taken that any heating processes applied to the structure causeas little volatilization of the respective photo-sensitive metals aspossible, in order to avoid mixing the metals upon their respectivecathode supports. After the .evacuation, the customary small quantitlesof hydrogen, rare gases or mixtures of gases may be added in the usualWay, with the usual tacts to the usual output circuits, or to theobvious modifications thereof.

The film record l4 may have three sound tracks l5, l6 and I1 thereon asshown, and an appropriate optical system may be provided for projectinglight through the sound tracks on to the respective photo-tube membersin theusual way.

The optical system may provide a long light bar covering all three soundrecords, in the usual manner. or three separate optical systemsrespectively cooperating with the three records and the cathodes may beprovided. 7 The members l2 and I3 then serveto prevent light from onerecord overlapping on to other cathodes than the one directly before therecord. The tracks upon the 1 record strip i4 may desirably compriseseparate ranges of the audible frequency range, or frequency spectrum.For instance, the record I5 may contain theifrequencies in the lowerthird of the audiblerange, the record l6 may contain the middle third,and the record [I the top third. For the purpose of dividing the audiblevibration range into such portions the audible frequency vibrationmembers may be used, or the frequency range may be divided in terms ofoctave, one range covering one-third of the number of eflective octaves,and the othertwo respectively the remaining thirds of the octaves.

,By this invention there is thus provided a new and useful photo-tube. IWhile there is here disclosed but a single embodiment of the inventiveconcept, it is possible to produce still further embodiments withoutdeparture from the spirit of the invention, and it is, therefore,desired that only such limitation shall be imposed upon the appendedclaims as arev stated therein or required by the prior art.

The invention claimed is:

spaced photosensitive electrodes respectively comprising diii'erent'photosensitive metals, light shields of insulating material respectivelypositioned between said electrodes and a cooperating electrode extendingparallel to said plurality of electrodes. 7

2. A photo-electric tube comprising a plurality of photo-sensitiveelectrodes respectively comprising different alkalij'metalaanda singleco operating non-photosensitive electrode.

3. A photo-electric tube comprising a plurality of photosensitive.electrodes respectively com.- prising sodium, potassium and caesium;and. a single cooperating non-photosensitive electrode. 4. Aphoto-electric tube comprising a plurality of sets of electrodesurfaces, one electrode. surface of each set being photosensitive, saidphoto.- sensitive surfaces being responsive to diiferent frequencyranges respectively. a V

' JANET F. LAW, Administratriw for Dufi C. Law, Deceased.

